package com.dreem.singleton.type3;

/**
 * @program: DesignParrtern
 * @description: 懒汉式（线程不安全）
 * @author: Peng
 * @create: 2021-01-22  10:47
 **/
public class Singleton03 {
    public static void main(String[] args){
        System.out.println("懒汉式，线程不安全   ");
        Singleton instance1 = Singleton.getInstance();
        Singleton instance2 = Singleton.getInstance();
        System.out.println(instance1 == instance2);
        System.out.println("instance1的hashcode() = " + instance1.hashCode());
        System.out.println("instance2的hashcode() = " + instance2.hashCode());
    }
}

class Singleton{

    private static Singleton instance;
    private Singleton(){}

    // 提供一个静态的公有方法，当使用到该方法时，才去创建instance
    // 即懒汉式
    public static Singleton getInstance(){
        if(instance == null){
            instance = new Singleton();
        }
        return instance;
    }
}